If you are going to be focusing on class structures in regards to Marxism then you could do the Great Gatsby - its relatively short. Or, possible Animal Farm(Revolution and class inequality) or Of mice and men (American dream for low social class workers who are migrants)- both short.Feminism maybe Jane Eyre- though this is long, The bloody chamber (but this is a collection of short stories), or maybe the colour purple?
It depends on what your focus is?